"My sons are identical, even to me," their mother, Tan Chaoyun, told the Chinese language paper News Now. "Even now, their father can't tell which one is which."

However, Chaoyun says the unusual haircuts were done mostly to help the teachers and fellow students identify their six-year-old children. Teachers at the school reportedly told the paper that the numerical haircuts have had a positive effect.

And the helpful haircuts could bring a little fairness to parental discipline administered by that confused father back at home.

"Sometimes, he punishes the second one for something the third one has done," Chaoyun said.

Quadruplet births are extremely rare, occurring when the mother's fertilized egg either splits twice, producing four embryos, or when the original egg splits and the second then splits as well.

The concept of "Hellin's Law," stipulates that one in every 89 pregnancies results in multiple births. But the odds for twins, triplets or quadruplets increase exponentially with each additional child. That means the odds of having quadruplets are about 1 in 700,000, or a 0.000142857143 percent statistical probability.